Fiber reinforced silicon carbide ceramics and method of producing the same

Abstract

It relates to fiber reinforced silicon carbide ceramics in which heat-resistant inorganic short fibers such as flawless SiC or Si 3 N 4 are three-dimensionally dispersed in a matrix composed of silicon carbide and entangled with each other to form a high strength shaped body as well as a method of producing the same. Further, it relates to high density silicon carbide ceramica in which metallic silicon is filled in pores of the shaped body, so that these fiber reinforced silicon carbide ceramics possesses both high strength and high toughness and are composite ceramics suitable as a heat-resistant structural material or a material with bio hard texture.

We claim: 
     
       1. A method of producing fiber reinforced silicon carbide composite ceramics, which comprises: (1) a step of wet mixing fine powder of silicon carbide with heat-resistant inorganic short fiber in order to three dimensionally and uniformly disperse the fiber and shaping the mixture to form a green shaped body;   (2) a step of impregnating the green shaped body with a solution of silicon carbide precursor and drying it to form a preliminary shaped body; and   (3) a step of heat treating the preliminary shaped body produced in the above step at a temperature of 800°-1700° C. to obtain a composite ceramic in which said heat-resistant inorganic short fiber is three dimensionally and uniformly dispersed in a high degree of entanglement throughout a matrix composed of said silicon carbide.   
     
     
       2. The method according to claim 1, wherein said preliminary shaped body is heat treated by hot pressing under a pressure in the above step (3). 
     
     
       3. The method according to claim 1, wherein at least a part of the impregnating, drying and heat treatments in the above steps (2) and (3) is repeated. 
     
     
       4. The method according to claim 1, wherein said heat-resistant inorganic short fiber is compounded into said matrix in an amount of 1˜45 vol %. 
     
     
       5. The method according to claim 1, wherein said heat-resistant inorganic short fiber is chopped fiber selected from the group consisting of SiC, Si 3  N 4 , ZrO 2 , Al 2  O 3 , C and 2SiO 2  3Al 2  O 3 . 
     
     
       6. The method according to claim 1, wherein said silicon carbide precursor selected from the group consisting of polycarbosilane, polysilane and polysilastyrene. 
     
     
       7. A method of producing porous, fiber reinforced silicon carbide composite ceramics consisting of silicon carbide and heat-resistant inorganic short fiber, which comprises: (1) a step of wet mixing fine powder of silicon carbide with heat-resistant inorganic short fiber in order to three-dimensionally disperse the fiber and shaping the mixture to form a green shaped body;   (2) a step of impregnating the green shaped body with a solution of silicon carbide precursor and drying it to form a preliminary shaped body;   (3) a step of heat treating the preliminary shaped body produced in the above step (2) at a temperature of 800°-1700° C.; and   (4) a step of filling in pores remaining in the shaped body with metallic silicon, at the time of the heat treatment of the above step (3) or after the heat treatment, to obtain a high density composite ceramic in which said heat-resistant inorganic short fiber is three-dimensionally and uniformly dispersed in a high degree of entanglement throughout a matrix composed of silicon carbide; and wherein metallic silicon fills in the remaining pores of the shaped body.   
     
     
       8. The method according to claim 7, wherein said preliminary shaped body is heat treated by hot pressing under a pressure in the above step (3). 
     
     
       9. The method according to claim 7, wherein at least a part of the impregnating, drying and heat treatments in the above steps (2) and (3) is repeated. 
     
     
       10. The method according to claim 7, wherein said heat resistant inorganic short fiber is compounded into said matrix in an amount of 1˜45 vol %. 
     
     
       11. The method according to claim 7, wherein said heat-resistant inorganic short fiber is chopped fiber selected from the group consisting of SiC, Si 3  N 4 , ZrO 2 , Al 2  O 3 , C and 2SiO 2  3Al 2  O 3 . 
     
     
       12. The method according to claim 7, wherein said silicon carbide precursor is selected from the group consisting of polycarbosilane, polysilane and polysilastyrene. 
     
     
       13. A porous fiber reinforced silicon carbide composite ceramic produced by the method of claim 7.